RAMSOIL, Risk assessment methodologies for soil threats

Abstract

Numerous methods are used to evaluate risks related to soil functioning. For five soil threats, viz. erosion, compaction, salinization, soil organic matter decline and landslides an EU wide inventory was made. In total, at least 26 official risk assessment methods (RAMs) could be clearly distinguished, while many other RAMs were basically similar and differed only in details. For instance, for compaction, most EU member states use deterministic models, which differed only in the level of detail, but risk indicators and the associated threshold values (i.e. risk perception) greatly varied. Some countries used e.g. a minimum saturated hydraulic conductivity (ranging from 10 to 24 cm d-1), whereas others used a maximum penetrometer value (ranging from 2 to 6 Mpa). In many cases there is a sound scientific basis to use different indicators and threshold values, but the validation of RAMs with field data is often poor, which makes it difficult to evaluate the appropriateness of indicators and treshold values. Also, in many cases RAMs simply developed independently with sometimes different purposes and therefore use different approaches. Notably, the implementation of official RAMs not only depends on the scientific basis of the RAM, but also on the acceptability (including costs) and the flexibility of the RAM. Harmonization of risk perception can be achieved through various activities ranging from synchronizing output data to prescribing complete RAMs. The first possibility is relatively easy but demands for extensive calibration and is therefore expensive. The latter possiblity is cheap but looses on geographical precision and public acceptance. Options for harmonization differ per soil threat, as is the maximum level of harmonization that can be achieved. This diversity is a function of the number of expressions of a soil threat (e.g. water erosion, wind erosion) and the nature of the expressions. Hence, it is unlikely that all soil threats can (or should) be harmonized up to the same level. In year 2 we will identify options for harmonization for each soil threat